Preheat your oven to 350 degrees Fahrenheit. Grease and flour two 9-inch round cake pans, or line the bottoms with parchment paper to ensure easy removal. Setting everything up before you start mixing ensures a smooth baking process.
In a large mixing bowl, sift together the flour, sugar, cocoa powder, baking soda, baking powder, and salt. Use a whisk to combine them thoroughly, ensuring there are no large lumps of cocoa or flour remaining in the mixture.
Add the buttermilk, vegetable oil, eggs, and alcohol-free vanilla extract to the dry ingredients. Mix on medium speed with a hand mixer or stand mixer until well combined. Be sure to scrape down the sides of the bowl to incorporate all the flour.
Reduce the mixer speed to low and carefully pour in the hot coffee or hot water. The batter will be very thin and watery, but this is exactly how it should look. This step is crucial for achieving the moistest possible cake crumb.
Divide the batter evenly between the two prepared pans. Bake for 30 to 35 minutes, or until a toothpick inserted into the center comes out clean. Allow the cakes to cool in the pans for about 10 minutes before transferring them to a wire rack to cool completely.
While the cakes cool, beat the softened butter until creamy, then gradually add powdered sugar, cocoa powder, and heavy cream until fluffy. Once the cakes are completely cold, frost the layers and the exterior. Add festive decorations like sugared cranberries or chocolate shavings to finish.
